RBTR 7D Silnylon

[Sam Farrington]

John,
Re: “I was talking about the 1.1oz Silpoly that weighs 1.24 oz/sq-yd.”

If  you haven’t already, check out RBTR’s fabric comparison chart at:

https://ripstopbytheroll.zendesk.com/hc/en-us/articles/236101568-Coated-Fabric-Comparison-Chart

The aged HH of the 20D, 1.24 oz riptstop silpoly[ester] is spec’d at 492mm.  IMO that is not acceptable for a tent.  And for me is not weight competitive with a 1.05 oz StoS 15D fabric, not to mention a 0.8 oz RW 7D.   Those conclusions are based on specs and Richard Nisley’s tests.  However, my bottom line reason for preferring better quality nylons like Dupont 6.6 over polyesters is experiences with nylons vs polyesters.  The polyesters have not held up, and that involves puncture and abrasion resistance as well as resistance to tearing.  If you have had better experiences with polyesters in this very light range, you may feel otherwise; but I have not.  The term, polyester, covers a very wide range of fabrics; so perhaps it could be manufactured to be as robust as nylon; but have not seen one yet.

Justin,
All my experience with making and modding tents involves sewing.    Honestly cannot envision tailoring curves on a tent using bonding for the seams. And the frustrated comments on BPL by Judy Gross of Lightheart Gear about bonding are not encouraging. If I were to go to bonding for tents, as distinguished from nearly flat tarps, I’d probably go whole hog like Henry Shires and use DCF. He  hopefully is making a living at it; but don’t see much enjoyment there.

Some may recall the “Big Dig” in Boston, in which a panel glued with an epoxy to the tunnel ceiling broke its bond and fell onto a passing auto, killing the occupant.

Right now, in the real, not virtual, world I’ve got a big roofing job to do with Grace Ice and Water Shield, and that will provide more than enough exposure to sticky adhesives, maybe more than I would want for an MYOG project.  Am looking for enjoyment, not frustration, in MYOG projects.

Granted, maybe it’s just that you can’t teach an old dog new tricks.

[Anonymous]

Sam, I wasn’t talking about not sewing…

What I was talking about, was some quick bonding before sewing to make the sewing easier with these very thin, very light, very gossamer type fabrics.  You can sew through the fusible, polyamide, material with no ill effect to one’s sewing machine.

Anyways, I’ve found that it makes sewing these fabrics a lot easier, hence why I mentioned it.

[Roger Caffin]

cannot envision tailoring curves on a tent using bonding for the seams.
I actually tried that with DP LiteSkin and their thermal bonding tapes.
The bottom line is that I eventually (over)sewed every joint with strong thread (bonded nylon).

You can sew through the fusible, polyamide, material with no ill effect to one’s sewing machine.
Here I agree with Justin. The stuff is good for that.

Cheers

[Sam Farrington]

Wow, you guys don’t collect any dust!
Anyway, by tailoring, I meant attaching fabric sections over or under a frame using fine pins. Once the fabric is taut on the frame, the whole thing is taken from the frame, the seam allowances are trimmed on the fabric panels, the seams are formed into lap felled seams, repinned, then sewn with the pins being pulled out just before they go under the needle. An example of the pinning process looks like this on a portion of an inner made of bug netting; but it is a similar process for a solid outer of coated fabric:

I can see how for a tarp, or a tunnel with rectangular fabric panels, adhesives might help before sewing, since the work can be laid on a flat surface. But for fabric panels with curved shapes and catenary seams, I’m not sure how the seam tapes could replace pins during the tailoring, as the initial pins hold the canopy-in-progress in position while the work is repinned, pin-by-pin, into lap felled seams for sewing.  It may seem laborious, but if no mistakes are made, goes fairly quickly; otherwise yes, it is a PITA to remove the thread from the seam and do it all over again; not to mention the weakening of the thin fabric by excessive pinning.

Roger, yes this is a ‘pop-up,’ but I’ve posted many times about other designs that allow the tent to pitch in the rain without water entering.  Granted, the above photo is not one of those; but thought it might help to explain what was meant by ‘tailoring.’  Hope to finish the current project, with some photos taken during construction, before the Earth is destroyed by an asteroid, or whatever.  .

[Roger Caffin]

Hi Sam

My tunnels do not have rectangular panels as the poles are tilted. Instead I mark the seams with a fine felt-nib pen and then pin the panels together in the hem region, just clear of the final seam.

I do not believe there is any weakening of the fabric if fine pins are used. I try to insert them between the threads anyhow – and then that needle comes along and really perforates the fabric.Seems to work so far.

Where I have used bonding tape was in sewing a silnylon edge to netting. Without a fabric edge the netting goes everywhere.

Cheers

[J-L]

Sam, I could be mistaken, but I think those results are for the first generation of 1.1oz Silpoly fabrics from several years ago. The second (current) generation seems to be much better. I can’t force water through the fabric at all, no matter how I try. There are a few tarp makers using the fabric now as well.

I’ve ordered a yard of the 7D RBTR fabric…will have to decide for myself which fabric to go with. The difference between the 7D fabric and a 30D silnylon for my tent design would be about 4-5 oz. I made some stuff-sacks using the 7D Rockywoods fabric about 3 years ago. I’ve noticed they get cuts more easily and are more subject to abrasion than heavier weight fabrics. Treated well though, they’ve held up nicely.

[Sam Farrington]

Roger,
It’s a bit of a nuisance, but I wrap the netting into the lap felled seams that separate the vestibule covers from the main tent. Just started doing that years ago because that’s the way better tent manufacturers did it. But where the netting joins the bathtub wall of the floor, I’ve just folded over the seam allowance, trimmed it, and sewed it to the floor with two lines of stitching so it looks from the outside like a lap felled seam, but isn’t, because the seam allowances are not overlapped inside. The problems of wear on the netting have not been where it joins the floor, but further up, so saw no need to do a true lap felled seam there.

John,
I took the info from the RBTR site just yesterday. Don’t know why they would not update the chart if it showed great improvement. The chart shows the HH as 1500mm before aging, which just meets the WP standard, so would not expect the fabric to leak water under pressure when new. But if RBTR’s age simulation is anything like Richard Nisley’s, the aged condition is what one would experience during most of the life of the tent. In any event, the vendor’s own acknowledgment of low HH is something I’d go by.

Agree with your concerns about the RW 7D nylon, and that is why I’ll limit it to a smaller fly that covers just the occupied area of the tent, so that it can be easily replaced as soon as it wears out. The rest of the tent outer will be the StoS 15D with sil/PU coatings, and that is what I’ll use for a replacement fly if the 7D does not hold up.

Not sure why you see the alternative to 7D nylon as 30D silnylon. The 20D nylon from Extrem Textil weighs under 1.1 oz; but there was a recent thread showing that it literally came apart at the seams. I finally got a yard of it from ET, and will do some lap felled seams on it and post the results. Will also contact Stephen S to see if he will HH test it, as I’ve no idea if it is the same 20D that Richard tested a few years ago. All that will take some time, as we are getting into the trekking and vacation season. The only other good alternatives in the 15-20D range that I know of have to be salvaged from tarps by StoS (Sil/PU) or Tera Nova (all sil, but very dark green). Granted, the cost of salvaging is high, but for just one tent well below the cost of a new tent. But would not be surprised if we see more durable fabrics coming on the market in the 15-20D range.

[Sam Farrington]

John,
Looking at the Lighthear Gear site, I ran across the following that might be of interest:

“Silicone coated polyester (also sometimes referred to as ‘sil-poly’. We are in the process of transitioning all of our ‘silnylon’ to this fabric over the next few years. This fabric is a 20D micro-ripstop polyester fabric. It is a little bit lighter weight than the 30D nylon, has the same High Hydrostatic Head of over 3000mm. It is absolutely waterproof, not breathable, and since it is polyester, it is more hydrophobic than nylon (absorbs less water when wet). Polyester will not stretch and sag like nylon will when cold and wet. It is a thinner fabric than the 30D nylon, and slightly more fragile, but with proper care, tents and jackets made of this fabric will last for many many years.”

As they are moving to sil-poly for all their tents, they might be willing to sell some. They have in the past.

[Sam Farrington]

Justin,
If you are interested in modifying sub one oz fabrics, you might be interested in a paragliding fabric,Porcher Skytex 27, a treated Dupont 6.6 ripstop nylon with a medium hand (not as stiff as DCF) that is 27 gm/m (about .8 oz/sq/yd. It appears to be very strong for such a light fabric, and now comes with greater water resistance.

I purchased some from Opale Paramodels in France, but now appear to have a UK site:
https://www.opale-paramodels.com/gb/fabrics-and-sewing/156-skytex-27-t2-3760245320666.html

There is a chat feature on the above linked page that might help with inquiries. I tried treating it with Walmart non-silicone sprays that adhered OK, but did not raise the HH. However, Graingers in the UK has some sprays that are for water proofing, not just DWR, that are highly rated.

Roger Caffin tested some of the original a few years ago, and it was not up to 1500mm or more HH. However, the 2d generation fabric, with an added layer of coating, would probably be waterproof, and still under one oz/sq/yd.

Just a thought should you want to experimnet. It might be far more tentworthy than the 7Ds mentioned here.

[J-L]

Sam, I was just referencing heavier fabrics as a baseline. 7D fabric might work, but 30D silnylon (for example) would definitely work and would produce a long-lasting tent. All other fabrics fall somewhere in between weight-wise. Options in between seem fairly limited though, besides using the Sea to Summit and Terra Nova tarps as you mentioned. For reference, here are those HH results:

https://backpackinglight.com/forums/topic/105800/

Good eye on the Lightheart Gear mention of silpoly fabric. I’ll have to ask them. MLD’s fabric also seems to be quite good and they are now using 20D silnylon on some products; however, when I last asked, MLD said they do not sell their fabric.

 

The RBTR 7D fabric arrived yesterday. Seems pretty good. Very soft and thin. I sewed a modified felled seam, similar to what Brendan describes here:

https://backpackinglight.com/forums/topic/73739/page/2/#comments

I was unable to tear the seam. Hole elongation seemed fairly normal. Just based on seam-strength and perceived waterproofness, it seems like the fabric would work for me. Good tie-out design and proper reinforcement will be key. I know people have been using Gossamer Gear’s tents with their 7D fabric to complete multi-month thru hikes, but this 7D fabric is just so thin! :) It would probably work fine, but I’ll have to think about it.

[Stumphges]

Has anyone made a fly or tarp with the RBTR MTN 6,6 silnylon?

[Sam Farrington]

I’ve some of the same reservations as John does about the RBTR 6.6 nylon 7D. If they could be overcome, would never make a tent with a fabric that either is or approaches black in color. Have posted about that already, but see below.

Hoping to finish some tests and update a thread from 2019 about Extrem Textil 20D silnylon. But will say now that even though I did see obvious fraying and unraveling when cutting sample pieces for Stephen Seeber to test. yet with even the original ET order, and a second larger order, have not been able to see these defects repeated. Am totally puzzled as to why. The OP on the 2019 thread revealed that the unraveling issue was solved, but not how. Anyway, will go into this when do the update.

The point is that the ET 20D weighs only .29 oz/sq/yd more than the RBTR 7D (1.06 minus .77). And the ET comes in lighter colors, is much stouter than the RBTR, and the HH is phenomenal, whether you look at Roger’s test or Stephen’s. When designing a tent that is a tension structure, like the Stephenson’s Warmlites, or Roger’s tunnel, there is a great deal of tension on the vestibule panels, and it is that tension that keeps the tent upright and taut, even when many guylines are used, because the vestibule panels spread the tension over a much wider area than a guyline does. This principle also applies to self-supporting tents that use vestibules in the same way, albeit the pole framework can lessen the pull force on the pegs to some extent.

Am not surprised that John’s RBTR 7D seams appeared to perform OK in a “modified” (mock?) lap felled seam. After all, it is a 6.6 nylon and stronger. But it is still very thin, has no body, and have trouble imagining it in a vestibule panel and remaining taut. Plus it will be the devil to work with. If I use 7D, it will be the lighter  Rockywoods gray. It is the PU coated side that sticks to itself, and this might be corrected with the right spray. Will experiment, but only outside in warmer weather (it’s still cold up heah) wearing the Minnesota Mining mask to protect against PFOAS. (NB: That is not the same as the COVID masks, that should protect both the wearer and bystander as well).

Am not ready to use RBTR 7D for the vestibule panels, and am not ready to sit in the dark when it’s still light, but raining and would like to be able to see what I’m doing while cooking and eating supper etc. without wearing a headlamp.  What frosts me about RBTR is carrying the fabric in black and almost black, and then having a photo on the product page that suggests that the charcoal is much lighter. Then to add insult to injury, the 1.3 oz 6.6 only comes in white; that’s right, white! AND, they have been promising forever that other colors are coming soon. From this and other developments, I wonder if their business plan has changed.

[Stumphges]

Sam, thanks for your thoughts. Various companies have been using 7D sil/PU nylons for pop-up flys and these are holding up OK. And one would think this 6,6 nylon without the weakening inner PU coating would be a good deal stronger. I’m interested in it in pyramid terms; maybe the tension would be too great, I don’t know.

But all your other points are valid. I’ve never had a black or dark gray tent. I was thinking it would be kind of nice, as light-colored ones can be little ovens, but I hadn’t thought about sitting in one all day during torential rains.

[J-L]

I think this 7D RBTR fabric would work for a tent fly (like a pop-up) and maybe in a small cat-cut tarp, but a pyramid tarp really stretches the fabric a lot on the bias – those long seams see the highest load and they’re all sewn on a bias. While it may be physically strong enough for a pyramid tarp, the fabric is really stretchy on the bias, so I don’t know how well it would turn out.

The lightest nylon fabric I’ve seen anyone use in a pyramid tarp is a 10D Sil-PU nylon by Locus Gear in their HB series. Locus Gear’s products are known to pitch very taut, but look at how much stretch there is at the mid-point ground-level tie-outs:

Khufu HB: https://locusgear.com/items/khufu-hb/?lang=en

And the even bigger Khafra HB: https://locusgear.com/items/khafra-hb/?lang=en

I do wish RBTR would improve their colors. Most seem either very dark or very bright. Where’s a light-gray or moss-green?

[Sam Farrington]

Stumphges,
I can’t stand to sit in any tent all day, but often take much longer to get ready and leave one in downpours. But at the end of the day, having a sheltered spot for meals is a big deal; so like big vestibules for cooking and storage. In the quest for gossamer weights, I note that inside space seems to be shrinking, even with the use of DCF. Doubt that we are anywhere near a tent that folds up as small as a softball and opens up to be the size of an igloo.

No doubt silnylon is more tear resistant if all silicone coated, but not sure I share concerns about having PU coat on one side. Some of the coats now are mixtures of sil and PU. We hear from Roger that ripping due to wind forces is rare. Punctures and abrasion would be larger concerns for me. But 6.6 is probably as good as it gets for nylon. It’s what they make hot air balloons from, albeit no doubt heavier than 7D.

John,
Well the bias is less than 45 degrees diagonal to the weave, but see your point. Don’t see how you could do a pyramid without seams at least partially on the bias, plus the cat cut seamns to take up the slack from the bias stretch. Looked at the pictures of Six Moon Designs’ Lunar Solo, which is 20D fabric, and the wrinkling is a lot more than I see on your links to the Locus site.

I only wanted to use fabric this light for a partial fly that would actually benefit from bias stretch to provide some greater space inside, and have less sag due to that stretch. Also, since the fly has few seams, could easily make another out of slightly heavier fabric if 7D is a flop. Roger said the fly could not be seamless and flat. Well OK, but it’s flat if folded in half at the line between the peaks, and am leaning toward vertical seams for the same reason pyramid fans like the vertical seams; that is, strength.

Since I’m not fluent with mids, don’t have much more to offer and will leave you to your druthers. I still don’t think a fabric, if otherwise good, should be rejected because it weighs 6/100 of an oz more than one oz/sq/yd. If that is an issue, maybe DCF is the only answer around.

If either of you do make a mid out of 7D, or even 10D or 15D, would love to see pictures.

[Roger Caffin]

>> We hear from Roger that ripping due to wind forces is rare.
Subject to how much UV the fabric has copped over the years. Standing tents are a BAD IDEA.

Cheers

[Stumphges]

Bias stretch is interesting, and might not be undesireable in some mid designs. Actually, the design I was thinking to roughly copy seems to rely on bias stretch. I have a couple cheap mids (a hex and an octagonal one) made by a company in Yunnan, China called “Knot” or “Ice River.” These use 20d silnylon that is rather lightly coated and seems fairly stretchy on the bias to me, although I don’t have enough experience to with other fabrics to really compare it.

Here is a link to the hex version, which they no longer make: https://www.aliexpress.com/item/32729098525.html

They’ve included a description  (scroll down) of how the hex is supposed to be a trigonal structure when the three principal ridges are staked out, and that then gets stretched along the biases into a hex shape as tension is applied to the second set of three ridges. I can tell you that the principle ridges are sewn selvedge-selvedge and the secondary ridges are bias-bias. Does this design necessitate the extreme cat cuts? Not sure, but you can see comparing some of the photos in that listing that if the edges aren’t pulled out too far, the cat cuts don’t look so extreme. (It’s also possible to find photos of Khufus that look like they’ve got excessive cat cuts, but it’s just that the owner has pulled the hem out too far.)

The hexagonal fly is about 600 grams. They’ve added three straps attached to the three principal tie outs, making this is easiest hex mid to pitch that I’ve used.

But it’s their octagonal design that I would like to copy in a smaller size. You can see one in one of the photos in that listing. I wrote about these mids some time back in this post, which has photos of the octagonal one: https://backpackinglight.com/forums/topic/tent-on-bias/#post-3501620

As you can see, the octagonal fly first pulls into a square shape that can fit a Supermid inner, then tieouts 5-8 are tensioned and the fly is pulled into an octagon.

What I like about these designs, and particularly the the octagonal one, is that pulling out that bias stretch creates a very taught, nearly cone shaped structure, which presents a very aerodynamic profile to the wind. Compared to the comparably sized Supermid, I think it would offer superior wind performance. In use, it hardly moves with 20-30 mph winds, even without using the mid-panel. I’ve not compared it directly to the Supermid, so I’m just guessing with this comparison.

And I don’t know if its the design, which seems to promote pulling all the bias stretch out of the panels, but these flys do not require retensioning when wet or cold, despite the fact that the fabric, being rather lightly coated, absorbs quite a bit of water.

I was thinking of using the RBTR 7D to make a smaller octagonal version of this as a 1+dog tent.

John, I see your point regarding the Locus Gear low-denier mids, but it seems like this company Knot has kind of based their designs around the natural tendency of rectangular mids to pull into pseudo-octagons. (This tendency was discussed in fascinating style by Robert Meurant in this post: https://backpackinglight.com/forums/topic/mid-set-up-issues-got-advice/page/2/#post-3443441)

The advantage of the octagonal design over the hex is that the former is much easier to pitch – just stake out a square. If the inner is also square, as is the one that comes with it, the octagon gives you four vestibules at corners 5-8.

But I have very little mid experience. Does anyone have an opinion on these designs and the advisability of copying them, with the 7D or other fabrics?

[Sam Farrington]

Those aliexpress tents are beautiful.  Not having the sophistication with geometry, and if I had access to one of those aliexi tents, I’d just set it up real taut, and trace the cat-cuts right off of it.  Assuming no changes in the orientation of the grain of my fabric, job done.

Unfortunately the lure of designing my own shapes doesn’t get me off that easily.

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